The role of the pineal complex in reproduction, thermoregulation, rhythmicity and behavior will be studied in appropriate species, including trout, alligator, lizard, rat and mouse. Through use of radioreceptor assay, melatonin receptors are to be characterized in several tissues, including rat testis and brain and trout retina and gill. The role of melatonin in temperature regulation of reptiles, both physiological and behavioral, will be investigated. Extra-pineal sources of melatonin, including retinae, are to be examined further.